Löwdin's Symmetry Dilemma in Correlated Systems: Green Functions Theory Results

POSTER

Abstract

The Hubbard model is a key system in the theory of strongly correlated electrons in solids, and it is realized with atoms in optical lattices. In the well-studied one-dimensional case, exact solutions are provided by analytic methods and density-matrix-renormalization-group (DMRG) simulations. In 2D and 3D, Green functions combined with many body approximations (GFMBA) present a reliable approach [1]. Here we present results demonstrating the capability of GFMBA to produce reliable data for the Hubbard gap energy despite its approximate character. We observed an improvement to the gap energy when lifting restrictions on spin symmetry and spatial homogeneity coupled with a spontaneous breaking of symmetry. This "symmetry dilemma" was described by Löwdin for Hartree Fock wave function calculations, and is extended here to GFMBA beyond Hartree-Fock [2].
[1] N. Schlünzen et al., J. Phys. Cond. Matt. 2020
[2] J.-P. Joost et al., Eur. Phys. Journal ST (2020), arXiv:2005.07651

Presenters

  • Sönke Hese

    • Institute of Theoretical Physics and Astrophysics, Kiel University, Germany

Authors

  • Sönke Hese

    • Institute of Theoretical Physics and Astrophysics, Kiel University, Germany

  • Jan-Philip Joost

    • ITAP, University of Kiel
    • University of Kiel
    • Institute of Theoretical Physics and Astrophysics, Kiel University, Germany
    • Univ Kiel
    • CAU Kiel, Germany

  • Niclas Schlünzen

    • ITAP, University of Kiel
    • University of Kiel
    • Institute of Theoretical Physics and Astrophysics, Kiel University, Germany
    • Univ Kiel
    • CAU Kiel, Germany

  • Michael Bonitz

    • Kiel University
    • ITAP, University of Kiel
    • University of Kiel
    • Institute of Theoretical Physics and Astrophysics, Kiel University, Germany
    • Institut für Theoretische Physik und Astrophysik, Christian-Albrechts-Universität zu Kiel
    • Univ Kiel
    • CAU Kiel, Germany

  • Claudio Verdozzi

    • Physics Department and ETSF, Lund University, Sweden

  • Peter Schmitteckert

    • HQS Quantum Simulations GmbH, Karlsruhe, Germany

  • Miroslav Hopjan

    • Institute for Theoretical Physics, Göttingen University, Germany